This invention relates to bending and forming segments of plastic pipe, for example, constructed from a polyvinyl chloride material, and more particularly, relates to a device for facilitating the bending of such pipe and for preventing distortion of the side walls of the pipe during the bending operation. While the invention is described with particular emphasis on the pipe bending use, those skilled in the art will recognize the wider applicability of the invention.
The prior art reveals a number of apparatuses useful for facilitating the bending and forming of plastic pipe. Usually, these devices have included means for heating the pipe to its forming temperature, after which the pipe is formed to the desired shape. Thereafter, the pipe is cooled to set the pipe in its new configuration. The apparatus for accomplishing these formative steps range from relatively simple devices which merely heat the pipe to the bending temperature, to complex apparatus that at least semi-automatically bend and bell segments of plastic pipe to form a desired elbow.
While these prior art devices work well for their intended purposes, they do exhibit deficiencies. For example, with the simplest type of apparatus, that is, one that merely heats the pipe to softening temperature, no control is available during the pipe bending operation. That is to say, often the pipe side wall collapses during the bending operation, rendering the bent pipe section unfit for use. In addition, resistance or infrared heaters aften overheat the pipe, resulting in distortion and pipe damage even before bending is attempted. Larger and more automated devices, on the other hand, are not adaptable to on-sight construction use, and require relatively long set-up times for converting from pipe size to pipe size.
Our invention eliminates these prior art deficiencies by providing a device that is portable for on-sight construction use, which remains an essentially closed system throughout its operation, and is more suitable for handling by field personnel than other known designs. A major advantage of our invention is that is provides controlled heating of the pipe or other structure along the entire length of the workpiece.
One of the objects of this invention is to provide a simple to operate, low-cost device useful in bending and forming plastic pipe or other structures.
Another object of this invention is to provide an expandable mandrel for insertion within the tubular structure of a plastic pipe, which supports the internal wall of the structure in its inflated state and prevents internal wall deformation during bending or forming.
Another object of this invention is to provide a device for facilitating plastic pipe bending and forming which includes an elastomeric boot having first and second diametric positions, the first position permitting insertion and removal of the boot along the internal diameter of the plastic pipe, the second position conforming to an internal diameter of the plastic pipe so as to support the internal side wall of the pipe during bending.
Yet another object of this invention is to provide an elastomeric boot insertable in a plastic pipe, the boot functioning both as a support for the plastic pipe and as the heat and coolant carrying medium for alternatively softening and setting the material from which the pipe is made.
Another object of this invention is to provide an elastomeric boot that can be used to expand the circumference of plastic pipe or structures, thereby forming a bell segment or other desired shape.
Another object of this invention is to provide a closed system apparatus for softening and supporting a plastic pipe during bend formation.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.